The Department for Child Protection is investigating how a child in state care became involved in a crime spree with three other youths, leaving all four facing a string of charges.
The teens, aged 13, 15, 16 and 17, have been charged with a string of offences including aggravated armed robbery, assault, motor vehicle theft, stealing and criminal damage after a tomahawk-wielding rampage in Carlisle and East Victoria Park on Sunday morning.
Police allege the group targeted four homes within 20 minutes, pushing over an 81-year-old woman and stealing an 84-year-old man's car in two separate incidents.
The group had earlier forced their way into a residence and assaulted three occupants.
They had also allegedly attacked a man outside his residence, but he managed to seek refuge inside his house, and it is believed one of the teens struck his front door with the tomahawk.
Police later found the elderly man's car abandoned.
Department for Child Protection acting director general Emma White said an internal investigation into the matter would be conducted.
"And certainly we'll continue to work very closely with police through their investigation," she told ABC radio on Tuesday.
Ms White said only a small proportion of troubled youngsters under state care were drawn back to dysfunctional families and friends, particularly when they reached adolescence.
That came despite the department's efforts to help them forge a productive life.
"We stick by these kids - we're on their tail, we take every opportunity to positively impact (their lives) and get them settled into safe homes or safe residential care options, and we're not always successful," Ms White said.
"Case managers really stick by them day by day."
Under certain circumstances such as self harm, young people could be kept in a locked facility for 21 days.
But while the victims were shaken and the community was disturbed by the age of the tomahawk-brandishing gang, troubled teens would not be under lock and key 24/7, Ms White said.
"That's simply not within our powers to do so," she said.
"They're still children."
Opposition child protection spokesman Stephen Dawson said the department's under-resourced staff were struggling to cope with massive caseloads.
"More children are coming into care with more complex needs and behaviours and there's no doubt the system isn't coping," Mr Dawson said.
"The Barnett government must increase funding so the community can be confident that vulnerable children are actually being protected."
Lee-Anne Smith, founder of HALO, a non-profit career and personal leadership development agency for Aboriginal youths, agreed more government funding was needed to address juvenile delinquency.
Ms Smith said she had noticed the age of young offenders had fallen.